Prematurity is the leading cause of neonatal morbidity and mortality in the United States. Intrauterine infections are an important, and potentially treatable cause of prematurity, and are associated with increased risk of neonatal white matter lesions of the brain and cerebral palsy. However, the mechanisms by which infection leads to prematurity and/or cerebral palsy remain speculative and treatment strategies untested largely because humans cannot be longitudinally studied following infection. We propose to use chronically instrumented pregnant rhesus monkeys at 120-130 day gestation with experimental intrauterine infection, as previously described (Gravett et al, Am J Obstet and Gynecol; 171:1660-1667,1994) to study the temporal and quantitative relationships among infection, cytokines, prostaglandins, steroid hormones, cytokine antagonists, preterm labor, and neonatal white matter lesions of the brain in order to develop effective interventional strategies. After postoperative stabilization in a tether, we will; (1) inoculate Group B Streptococci (GBS) into the amniotic fluid to establish intrauterine infection and preterm labor. Uterine contractility will be continuously monitored and periodic samples of amniotic fluid and maternal and fetal blood (1-4 cc) will be obtained for assays of eicosanoids, steroid hormones, cytokines, matrix metalloproteinases and for microbial studies; (2) utilize antibiotics with and without potent inhibitors of proinflammatory cytokine production (dexamethasone,IL-10) o prostaglandin production (indomethacin) to ascertain the most effective intervention to down-regulate the cytokine/prostaglandin cascade and associated uterine activity; (3) infuse proinflammatory cytokine IL-1beta into the amniotic cavity through indwelling catheters in the absence of infection. Prior to infusion of IL-1beta in the absence of infection, specific novel proinflammatory cytokine inhibitors (IL-1ra and sTNF-R1 PEG) will be used to identify other potentially useful immunomodulators. Samples of the decidua, fetal membranes, tissues, and brain will be obtained at cesarean section for microbiologic, histopathologic studies, immunohistochemistry for cytokines, localization and quantitation of mRNA for cytokines and PGHS-2. Fetal brain will be examined for increased apoptosis associated with white matter lesions. Leukocytes in amniotic fluid and tracheal aspirates will be assessed by flow cytometry Postpartum, the mother will be treated with appropriate antibiotics to eradicate the GBS from the genital tract and returned to the colony. These studies will clarify the pathophysiology of infection-associated preterm labor and will suggest effective interventional strategies.